Microstructure and mechanical properties of Mg-xLi-3Al-1Sn-0.4Mn alloys (x = 5, 8 and 11 wt%)

Effects of Li addition on microstructure and mechanical properties of as-cast and as-extruded Mg-xLi-3Al-1Sn-0.4Mn alloys were investigated. Mg-3 wt%Al-1 wt%Sn-0.4 wt%Mn alloys with different Li addition (5, 8 and 11 wt%) were cast under an SF6 and CO2 atmosphere at 700 °C and extruded at 200 °C. Li addition to Mg-3Al-1Sn-0.4Mn resulted in the formation of MgLi2Sn and MgLi2Al intermetallic compounds and random basal texture. With increasing Li addition from 5 to 8 and 11 wt%, ultimate tensile strength was decreased from 258 to 240 and 220 MPa. On the other hand, the elongation was improved remarkably from 16.0% to 15.4% and 35.1% at room temperature due to transformation from HCP to BCC crystal structure and a weaker basal texture. In the Mg-xLi-3Al-1Sn-0.4Mn alloys, MgLi2Sn and MgLi2Al intermetallic compounds played a significant role for the increase of the mechanical properties.